Si3 N4/SiO2 Multi-Layer Reflecting Stacks for Photonic Switching Applications

Abstract

AbstractWe have fabricated stacked-structures comprised of i) fused silica substrates, and ii) near-periodic Si3N4/SiO2 bi-layers by low-temperature, 250°C, remote plasmaenhanced chemical-vapor deposition. Comparing the reflectance of these structures with model calculations, we have been able to identify the effects on the reflectance spectra of departures from i) exact periodicity, ii) not having the constituent dielectric layers each posses an ideal optical path length, OPL, exactly equal to λcentral/4, and iii) the intrinsic dispersion in the dielectric functions of the oxide and nitride materials. We have prepared quasi-periodic structures in which the OPL of the higher index Si3N4 layer was > λcentral/4, and in which the OPL of the lower index SiO2 layer was < λcentral/4. This promotes a second strong reflectance band at an energy that is approximately two times that of the primary band. Calculations have shown that the reflectance values in this band, and near a reflectance minimum on the high energy side of the band, are both very sensitive to changes in the optical properties of the nitride film. We present calculations that demonstrate the effects on the reflectance of this band by a temperature-induced modulation of the optical properties of the oxide and nitride layers.